Double-hot-chamber furnace



0. A. COLBY.

DOUBLE HOT CHAMBER FURNACE.

APPLICATION man DEC. M. 191a.

1,347,896 Patented July 27, 1920.

WITNESSES: INVENTOR MJWMW Or A (o/by 1 7 7 63% ATTORNEY UNITED STATES PATENT OFFICE.

01m A. coLiaY. DEA-IRWIN, PENNSYLVANIA, ASSIGNOR To wnsrmcnousn ELECTRIC a MANUFACTURING COMPANY, A conroaArroN or PENNSYLVANIA.

DOUBLELHOT-CHAMBER FURNACE.

Specification of Letters Patent.

Patented July 2'7, 1920.

Application filed December 14, 1918. Serial No. 286,718.

To all whom it may concern:

Be it-known that I, ORA A. COLBY, a citizen of the United States and a resident'of Irwin, in the county ofwestmoreland and State of Pennsylvania, have invented a new and useful Improvement in Double-Hot- Chamber' Furnaces, of which the following is a specification.

My invention relates to electric furnaces and particularly to high-temperature electric-resistance furnaces for heatingand treatin metals that maybe operated continuous y for comparativelyv long periods Of time. i L

One object of my inv ntion is torpr'ovide a high-temperature -elee'etric-res'istanee?v furnace that will have several associatedheaiv in chambers so arranged'as'to require a:

minimum number of parallel-connectedre sistors to generate the necessary'heat. Another object isto. obtain a high thermal efiiciency with a small. furnace .ofthis type. A

Another object of my. inventionis to prlrlr' t e:

vide an arrangement that will' brin connections between the metal-termlna connectors and the carbon electrodes at a dis-' tance from the heating .chambers and that will allow of covering theconnections with finely divided granular material to prevent the air from coming into contact with the joint between the two'materi'als.

In a copending patent Thornton,J r. and O. A.

198,275, filed ea. 24., 1917,

ing chamber, the top and bottom walls of the heating chamber bein resistors of the furnace- One feature 'ofmy invention consists in sowlocatmg an additional heating chamber as to require an in energy input to the ra ating surface. By increasing theenergy Input 1n thedouble hot-chamber furnace without materially in-- creasing the radiating surface, the thermal efliciency will be increased.

When the carbon electrodes, to whlch the a lication of Ciblby, Serial No. is shown and de-;

scribed an electric-resistance furnace hav-' ing a single heating chamber and a pre-heat-' made 'of blocks.

of carbonaceous material t iat'constitute the t I scribed.

metal terminal plates in this type of furnace are attached, arelocated close to the heating chamber, they may become heated to such a high temperature as to cause the surface of the electrodes to oxidize and crumble away; Such action will: result in poor contact between the metal plate and the electrode and, if such heating is long continued, arcing may take place between the two, causing a stilLfurther deterioration lIl thequalit of the contact. By locating these electro es and the joints substantially away from the furnace chamber proper, the temperature rise will be kept down and, by covering them with finely divided granular material, theoxidation will, to a great extent, befipreven'tedw The above and other objects and the novel features of the invention will be apparent from the followingdescription taken in connection with'the accompanying drawing that forms a part of-this application and in which Figure 1 is a vertical,' transverse, sectional view of an=electric-resistance furnace embodying my invention; Fig. 2"-is a sertional viewof-thefurnace shown in Fig. 1 taken on the'line IIII of Fig. 1, and Fig. 3 is a front view of a furnace embodymg my invention. r i

A Referrinn -to Figsul and 2, the furnace construction comprises a suitable iron frame work and exterior shell 10 that carries the vertical walls .11 and bottom wall 12 of refractory material, the latter supporting a refractory-brick base structure 13. A -eenter wall 14 is spaced from theside walls-11 to form hoppers 15 into which granular material, such as graphite or coke, may be charged fora purpose to be de The ho pers 15 extend downwardly .into the urnace structure and in each of them is a solid terminal electrode 16 for leading current to the resistors. The electrodes 16 are located at the outer sides of the 'hop ers 15 near the bottom ends thereof an rest on extensions 17 of the same material that are connected, at their outer ends, to metal terminal plates 18. The terminal plates 18 extend downwardly throu l1 the'fioors of boxes 19 thatare at- Masses of ranular material 22, consisting of fine sent or silica, are employed to cover the joints between the metal terminal plates 18 and the electrode extension 17, thus re venting the air from coming into co'ri act with, and deteriorating, the joint between the two members.

The main heating chambers 23 of the furnace are open at one end and otherwise inclosed by to and bottom walls 24, 25 and 26 separate by spacers 27 that form the side walls of the heating chambers. The walls 24, 25 and 26 consist of carbonaceous materials such as silicon-carbid bricks or slabs, and the intermediate spacers 27 may also consist of such blocks but any highly refractory material will serve the purpose, since it' is not necessary that these spacers be of electrical conducting material.

The walls 24, 25 and 26 constitute the resistors of the furnace that are spaced from the terminal electrodes 16. The spaces between the electrodes and the resistors are filled with masses 28 of granular gra bite or coke packed to provide a medium etween the electrodes and the resistors that is an electrical conductor and also a thermal insulator that is of greater cross section than the resistor to prevent overheating-and consumption of the expensive electrodes 16. The masses 28 oxidize and are gradually consumed and may be replaced by additional material introduced and tamped into the upper ends of the hoppers 15.

The wall 25 forms the floor of the upper heatin chamber 'and the top wall of the lower eating chamber. A space 29 is provided above the resistor 24 and a similar space 30 is provided below the resistor 26 to more effectively insulate the two heating chambers from the top and the bottom surfaces of the furnace. These air spaces serve to retard leakage of heat from the resistor blocks 24 and 26 and, since the resistance of carborundum changes slowly at high temperatures, the three sets of blocks constitutmg the top and bottom walls of the two chambers, after a few hours run' and heat interchange, will have approximately the same resistance and, eventually, will have approximately the same temperature. Spacers 31 form the side walls of the 5 aces 29 and 30 and these may consist of sma l blocks of carbonaceous material but an highly refractory material will serve t a purpose. Within the fire-brick base 13 is mclosed a preheating chamber 32 underneath the lower of the twh heating chambers 23 and separated from the latter by the air space 30 and a layer of the refractory material 13. The preheating chamber 32 is thus so located that it will derive heat from the wall 26, which loses fart of its heat through the air space 30 an the one layer of the refractory material 13. Cold articles, such as cold pieces of metal, would be damaged if intrdduced directly into thc high-temperature heating chambers 23 and they are. therefore, first heated to a moderately high temperature in the preheating chamber 32, after which the may be introduced into either of the hig temperature chambers 23.

Temperatures up to about 1200 C. may be obtained in this furnace without diffic'ulty, and the furnace is adapted to be used with success for hardening tool-s and dies and for firing porcelain. A non-oxidizing atmosphere may be obtained within the fur nace by spreadlng granular charcoal or carbonover the floors 25 and 26 near the doors where it is burned by the enterin air;

\Vhile I have shown and descri ed my invention in detail, it is understood that numerous changes and adaptations may be made without departing from the spirit of my invention and I desire, therefore, that only such limitations shall be imposed as plying heat to all of said chambers, one of the said resistors constituting the floor of the up or chamber and the top wall of the lower ieating chamber.

4. An electric furnace comprising two heating chambers and a preheating chamber in vertical alinement. said heating chambers having top and bottom walls formed of blocks of refractory electrical-conducting "material constituting the resistors of the furnace the bottom wall of the up er heating chamber forming the top wal of the lower heating chamber.

5. An electric furnace comprising two heating chambers and a preheating chamber in vertical alinement and resistors disposed to form the to and bottom walls of both of said heating 0 \ambers and blocks of refractory material for separating the top and bottom walls of said heating chambers. 6. In an electric furnace, the combination with two superposed heating chambers, of

resistors adjacent the same comprisin solid blocks of refractory electrcal conucti material in contact with one another an forming the-top and bottom walls of said chambers, terminal electrodes, and a mass of thermal-insulating and electrical-conducting granular material interposed fbetween each of the electrodes and 'theends of the resistor to prevent overheating o'f'the'electrodesZ-fl" '7, In an'electric furnace, the'combination with two'superposed heating chambers, and a preheating-chamber, of resistors comprising soli d blocks of refractory electrical oonducting material in contact withon'e another and forming certain walls of said chambers, hoppers on opposite'sides of said chambers, terminal electrodes in said hoppers, and a mass of thermabinsulating and electricalconducting material between each of said electrodes and the resistors and of greater cross-section than the resistor to prevent overheating of the electrodes.

8. In an electric furnace, the combination with two superposed heating chambers having walls formed of blocks of refractory electrical-conducting material constituting the resistors of said furnace, and a preheating chamber, of hoppers on opposite sides of said chambers, solid carbonaceous terminal electrodes in said hoppers, and a mass of thermal-insulating and eleotrical-conductin material between each of said electrodes an the resistors, said masses of material being granular and of greater cross section than the resistor to prevent overheating and consumption of the electrodes.

9. An electric furnace comprising two superposed heating chambers each having an open end, top and bottom Walls formed of solid refractory electrical-conductin mate rial that constitute the resistors of t e furnace, and side walls of refractory material for separating the top and bottomwvalls.

10. An electric furnace comprisingtwo superposed heating chambers having top and bottom walls formed of blocks of refractory electrical-conducting material constituting the resistors of the furnace,

11. An electric furnace comprising resistors consisting of blocks of electricalcondncting refractory material inclosing two associated spaces which constitute the heating chambers of the furnace, terminal electrodes, and a mass of thermal-insulating and el.ectrical- 'onducting material between each of said electrodes and said resistor, said masses of conducting material being granular and of greater cross-section than the resistor to prevent overheating and com sumption of said electrodes.

12. An electric heating furnace comprising two superposed heating chambers, a preheating chamber, and a resistor between said preheating chamber and one of said heating chambers and arranged to supply more heat to said heating chamber than to sand preheating chamber. 0

13. An electric heating furnace comprising two heating chambers and a preheating chamber in vertical alinernent, and resistors, one part whereof is disposed between said preheating chamber and onset said heating chgnnbers and "closer to the heating-chamber than to the preheating ch mber as to sup y. more heat to are fdrmer thafi'to this laden #w- UMP-H! I-ILL" isr-valuiala-ri luv:

'14. An electric 1 ifui'na'c'e "cbmpi'isihg two renting-chambe s and a preheating camber "i vertical aunt-meat, and rss'isterssnavm one part' disposed bet een Q's'aid in'g eh'almb'er ariil s'aiii preheating --killl-iffll5ei "as constituting a wall for the heating cham her, and a layer of material for separating said heating chamber from said preheating chamber.

15. An electric furnace comprising two heating chambers and a preheating chamber in vertical alinement, resistors having one part disposed between said heating chambers and constituting certain walls of said heating chambers and having another part disposed between said heating chamber and said preheating chamber and constituting a wall of said heating chamber, a layer of material for separating said heating cham her from said preheating chamber, terminal electrodes on opposite sides of said chambers, and a mass of electrical conducting material between each electrode and said resistors.

16. An electric furnace comprising two heating chambers and a preheating chamber in vertical alinement, resistors having one part constituting the floor of the upper heating chamber and the top of the lower heating chamber, another part constituting the floor of the lower heating chamber, a layer of material of low thermal and electrical conductivity between said lower resistor and said preheating chamber, hoppers at opposite sides of said resistors, terminal electrodes in said hoppers, and a mass of electrical conducting thermal insulating granular material between each electrode and the resistor adapted to prevent overheating of said electrodes.

17. An electric furnace comprising two heating chambers and a preheating chamber in vertical alinement, resistors for supplying heat to all of said chambers, hoppers on opposite sides of said chambers, terminal electrodes in said hoppers, lateral projections on said electrodes for connecting to terminal connectors, and masses of granular material for covering the end portions of each of said lateral extensions.

18. In an electric furnace, the combination with a heating chamber, a preheating chamber and resistors for supplyin heat to all of said chambers, of means or reducing the amount of heat conducted away from said resistors and said chambers.

19. In an electric furnace, the combination with two heating chambers, a preheating chamber and resistors for supplying heat to all of said chambers, said chambers and resistors being in vertical alinemcnt, of juoketing means in alinement with said chambers and said resistors for reducing the amount .of heat conducted away from said resistors and said chambers.

20. In an electric furnace, the combination with two heating chambers and a preheating chamber in vertical alinement, said heath? chambers having top and bottom 10 walls 0 mood of blocks of refractory electriad-conducting material constituting the resistors 01 the furnace, of jacketing means located above said heating chambers and below said preheating chamber for reducing the amount of heat conducted away from said resistors and said chambers.

In testimony whereof I have hereunto iglfgcribed my name'this 30th day of Nov.,

ORA A. COLBY. I l 

